1. Field of the Invention
The present invention relates to a fuel delivery device of a fuel tank for a vehicle, which supplies fuel to an engine.
2. Prior Art
A conventional fuel delivery device comprises, for example as shown in U.S. Pat. No. 5,447,175, a float chamber having a float valve within, a sub chamber having a mesh filter within and a communication chamber for communicating therebetween. When the fuel in the fuel tank is sufficient, since the float valve comes up and a main fuel introduction inlet is opened so that the float chamber and the communication chamber are communicated to each other, the fuel within the fuel tank is sucked to the communication chamber and a fuel pump through the float chamber and further is supplied to the engine. However, when the fuel is decreased, the float valve comes down and the main fuel introduction inlet is closed so that the suction force by the fuel pump is applied to the sub chamber and a small quantity of fuel remaining in the fuel tank is sucked through a fuel suction conduit so as to be introduced to the sub chamber, thereafter the fuel sucked from the sub chamber to the communication chamber and the fuel pump is supplied to the engine.
In the example disclosed in U.S. Pat. No. 5,447,175, a function of the float valve within the float chamber is mainly improved and no particular attention has been given to the sub chamber. However, immediately after the suction of the fuel to the communication chamber is switched from the float chamber to the sub chamber, air (containing a gasified fuel) collected in the sub chamber is sucked to the communication chamber and is often fed to the fuel pump and the engine. Further, after the fuel is sucked from the fuel suction conduit, air comes into the sub chamber together with the fuel and the air is sucked to the communication chamber in a similar manner to that in the above case so that there is a risk that air is supplied to the fuel pump and further to the engine. This means that an appropriate mixture of fuel and air can not supplied with respect to the engine and this causes a trouble in an output of the engine.
Since a small quantity of fuel remaining in the fuel tank is sucked to the sub chamber, it is easily expected that air is sucked to the sub chamber together with the fuel. However, it is difficult to suck only the fuel with completely removing the air and if it is desired to achieve this, this achievement causes an increase of a cost. Since the more the fuel tank becomes flat, the more the fuel suction at a time when the liquid surface of the fuel is swung fuel sucking (to the engine) becomes unstable, such a suction of air easily occurs.